Making vinegar from scratch can be such a sinch, and coupled with its indispensability in the kitchen, makes it a worthwhile endeavor. The process of getting to vinegar is simple:
- start with a sugary liquid
- let the sugars ferment into alcohol by way of our friendly local wild yeast
- then with continued air exposure the alcohol will be eaten up by native acetobacter making it into vinegar. Boom!
An even simpler overview:
- crush fruit in your fermentation vessel of choice
- leave it be until it tastes like vinegar.
- strain the solids. So easy!
What can be made into vinegar?
Damaged fruit and vegetables, including scraps like cores, skins and other odds and ends are excellent candidates for turning into vinegar. High sugar content is helpful, though there’s way to make it out of just about anything.
Step 1: Preparing the mash
Choose what you would like to make vinegar out of and then make a puree out of it. If your ingredients can’t provide enough liquid themselves, it’s okay to add water until it becomes a loose slurry. However keep in mind that our goal is to have as much sugar as we can, as it’ll impact the strength of the final vinegar. If you add water you may want to consider adding some sugar as well. More on that below:
Controlling the final acidity of your homemade vinegar
Being able to control the final acidity of our vinegar will help us ensure a smoother transition with less fungal threats and provide us with a consistent product to rely on for our culinary projects. Generally the vinegar we buy from the grocery stores are 5% acidity.
The percentage of acidity is roughly the same as percent alcohol. That means a 5% alcohol can make about a 5% acidity vinegar. Since the sugars present in our original mixture will ferment into alcohol, the amount of sugar then is directly responsible our final strength of acidity.
sugar –> alcohol –> vinegar
I use a hydrometer I bought for $20 that measures sugar in liquid through Brix. 1° Brix is about 0.5% alcohol. Additionally my napkin math says that 12g of sugar per a quart of liquid equals 1 brix, so 24 grams equals 1% alcohol, aka 1% vinegar. That estimate can be handy to bulk up the potency of your vinegar, balance a watered-down mixture, or if you want to make vinegar from something that doesn’t really have any sugar to offer, such as celery.
Step 2: Fermenting
Once you have your sugar content in order, now comes the fine art of wild fermentation. In order to employ the native wild yeast you really don’t have to do anything. The common line of thought is to place a cloth over the top of your fermentation vessel, fixed on with a rubber band or string so there is a constant contact with air. However when using ripe fruit or old vegetables I just place a loose fitting lid over the container. The wild yeast are likely well colonized already on your ingredients that all you really need to worry about is the off-gasing from the fermentation not blowing off the lid. When I used to employ the cloth-cover technique my vinegar mixtures often would dry out before they completed.
Either way, there should be some bubbling activity of the wild yeast converting the sugars into alcohol within a few days. To expedite this process simply stir the mash occasionally to incorporate air. Also, keep in mind that the temperature during the fermentation will affect its speed. The warmer the faster.
Once the bubbling subsides, the yeast will have consumed as much sugar as they can and you’ve achieved maximum alcohol. At this point you can strain out the solids. Exposure to air is more important now than it was before. Acetobacter cruise the air looking for alcohol to devour up, and we hope they do. Basically our goal now is to make our alcoholic beverage “go bad.”
Finishing the vinegar
So let’s say you’ve pureed or mashed your fruit, altered the sugar content to your preference, and let it ferment to its heart’s content. Now the bubbling has subsided, which means the wild yeast have consumed all the fermentable sugars available to them and you’re at max levels of alcohol content. When does the vinegar happen?
That part, if doing naturally through wild methods is up to nature. It can sour immediately or may take weeks, or even months to do. And the only way to know is to periodically taste it. Now, there is a trick if you want to push it along. Acetobacter loves to hang out, so if you introduce it, it will find your alcohol party. You can be casual and leave an open container of vinegar next to your soon-to-be vinegar, or you can pour a splash in like a starter culture. Either way, shoot for a raw vinegar to do it with.
One final important note for once you finally have achieved your vinegar and it’s delicious and sour to you. Put a lid on it. Our natural, raw vinegar will actually disperse its acidic acid into the air overtime and eventually become a dull, faintly flavored water. Just toss it in a mason jar with a lid or similar and it’ll last a long long time.
What if weird things begin to grow on it?
The cool thing about vinegar, especially if we make sure to make one with sufficient final acidity is that once it becomes vinegar it’s no longer a hospitable environment for insects and mold. Consider how vinegar is used as a natural cleaner. I have heard of many cases, and then done my own vinegars, that were left in an open container with no cover and allowed to progress as nature willed it. After enough time I pulled off the gnarly top and had wonderful vinegar underneath. Not that I’m recommending this to anyone, but what a fun story to tell.
Most likely if your fermenting mash develops a growth it will be a white film called kahm. Do not despair, kahm is harmless, and is typically a product of lower sugar levels. You can always add more sugar, but when the vinegar finally develops it’s likely the kahm will die and settle into the lees.
When in season tomatoes are a great candidate for vinegar. I slice and crush my overripe and split heirloom tomatoes. The last time I did this I got a reading of 6 Brix and the tomatoes provided plenty of their own liquid. If I ferment until all bubbling activity has ceased (0 Brix) I’ll get a 3% alcohol tomato “wine.” So letting that continue it’ll be a 3% vinegar. That’s not too bad, and I can assume even if you don’t measure, if you’re using ripe tomatoes you’ll get something similar. If I wanted to shoot for 5% acidity I could just add 48 grams of sugar to my quart of mashed tomatoes to get that additional 2% more.
Puree enough celery for a quart of mash. This will vary but may take roughly one full head, then top it off with water just enough to cover. Stir in 120 grams of sugar until it is dissolved. Then on with the fermentation.